All indices use January 1, 2004 as a baseline from which a seven-day moving average is calculated. So if you look at auto buyers, you will see a more or less predictable seasonal car-buying pattern, peaking during the late spring and summer when people are looking at the new models and dealers cut prices on last year’s stock. The number of searches for cars falls off around the winter holidays before ticking up again at the end of the year, presumably for tax reasons.